<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">

function boom()
{
  var tbody = document.getElementById("tbody");
  var trX = document.createElement('tr');
  tbody.insertBefore(trX, tbody.getElementsByTagName("tr")[0]);
  var trY = document.createElement('tr');
  tbody.insertBefore(trY, trX);
  var tdY1 = document.createElement('td');
  tdY1.setAttribute('rowspan', 0);
  trY.appendChild(tdY1);
}
</script>
<style>
td {width: 30px; height: 30px;}

</style>
</head>

<body onload="boom();">
 <table border cellspacing="10px" cellpadding="10px">
  <tbody id="tbody">
   <tr>
    <td></td>
   </tr>
  </tbody>
 </table>
</body>
</html>
